Network elements in data and telecommunications systems typically include multiple interconnected modules or line cards, such as through a backplane, a mid-plane, or the like. Network operators add modules as required for increased capacity or features. Typically, all network elements require a controller module which generally provides operations, administration, maintenance, and provisioning (OAM&P) of modules within the network element. The controller module can also include a data communications channel to a network and to an element management system (EMS) and the like. In a switch network element, such as an optical switch, Ethernet switch, SONET/SDH switch, and the like, there is also typically a switch fabric module configured to provide switching between line modules, port modules, or the like.
Switching systems and network elements typically require redundant, replaceable equipment for controller and switch fabric modules. This is required to provide carrier-grade performance and reliability, i.e. to ensure network element operation without a single point of failure and to provide system availability above 99.999% or more as required. Traditionally, controller and switch fabric modules are deployed with redundancy, such as with a 1:1 protection (working plus protect) or a 1:N (one protect for N working). Note, in protection schemes, protect is also referred to as standby or secondary, and working is also referred to a primary or active.
Referring to FIG. 1, a block diagram illustrates two conventional protection mechanisms 10,12 for switch fabric modules 14, controller modules 16, and combined switch fabric/controller modules 18. In these examples, all of the modules 14,16,18 are interconnected through a backplane 20. Alternatively, these modules 14,16,18 could be interconnected through other mechanisms as are known in the art. The protection mechanism 10 includes 1:1 or 1:N switch fabric modules 14 and 1:1 or 1:N controller modules 16, i.e. switch fabric and controller modules are separate modules. Here, there is a separate working and protect module (or N working for one protect) for each of the switching and control functionality. The mechanism 10 provides full redundancy, but requires a large number of replaceable modules increasing cost and utilizing excess space on the backplane 20. For example, a 1:1 scenario here requires four modules which in a network element shelf could occupy four slots which could be instead utilized for traffic carrying modules.
The protection mechanism 12 includes 1:1 or 1:N switch fabric/controller modules 16 which combine both the switching and control functionality. This combination of functionality reduces the required space. However, when one of the modules 16 fails, it can result in a double failure losing both switching and control functions. In this case, the switch configuration information must be persisted on the standby control component so that the standby fabric can be rapidly configured. This requires updating the standby control component whenever a switch configuration change takes place on the working module—i.e. the standby control component must be kept in-synch with the working control component. This can introduce design complexity and the risk that the working and standby become out of synch leading to a traffic loss on a protection switch.